Rockable breech bolt locking block



Feb. 25, 1958 L. R. CRITTENDON ETAL ROCKABLE BREECH BOLT LOCKING BLOCK 4 Sheets-Sheet 1 Original Filed Jan. 19

IN V EN TORS Feb. 25, 1958 l.. R. cRrrTl-:NDON ETAL 2,824,400

ROOKABLE BREECH BOLT LOCKING BLOCK Original Filed Jan. 19. 1955 4 Sheets-Sheet 2 G NSK G E Feb. 25, 1958 L.. RycRlTTENDoN ETAL ROCKABLE BREECH BOLT LOCKING BLOCK Original Filed Jan; 19, 1955 4 Smets-sheet s s, MM, SK

1N VEN TORS EX/E 19A YCR/TTE/VDO/V EL L/S WILL/AH HA/LSTON Feb. 25, 1958 L R. cRlTTENDoN ETAL n 2,824,400

Y RocxABLE BREECH BOLT LOCKING BLocK Original Filed Jan. 19, 1955 4 sheets-Sheet 4 RocKAnLE Bannon nom LOCKING BLOCK Lexie Ray Crittenden, Wilmington, Del., and Ellis William Hailston, Ilion, N. Y., assignors to Remington Arms Company, inc., Bridgeport, Conn., a corporation of Delaware Original application January 19, 1955, Serial No. 482,726,

now Patent No. 2,751,702, dated June 26, 1956. Divided and this application February 8, 1956, Serial No. 564,249

8 Claims. (Cl. 42-16) This invention relates to an improved breech loading magazine firearm of the type characterized by a rearward sliding breech block.

This application is a division of application Serial Number 482,726, filed January 19, 1955, now Patent No. 2,751,702, issued lune 26, 1956.

The principal object of this invention is to provide for improvements in the certainty and accuracy with which cartridges are transferred from magazine to barrel chamber, thereby avoiding malfunctions due to failure to feed, etc., and securing increased accuracy through the avoidance of bullet deformation on feeding.

Another object is the provision of improved means for the manual operation of the rearward sliding breech block and for securely locking such a breech block in position to close the breech end of a barrel.

Other important objectives are improvements in safety, in smoothness and speed of operation, and in economy of manufacture.

We contemplate that we can best achieve certain of these objectives by arranging our design to utilize tothe maximum extent components which are common to other production firearms, for example, the fire control assemblyshown in U. S. Viatent No. 2,675,638, issued on April 20, 1954, to L. R. Crittendon and utilized cornmercially by applicants assignee in an auto-loading shotgun, a slide-operated shotgun, and a slide-operated center tire riiie, as well as the present design. Others of. these ,objectives are achieved by the use of a die cast receiver so formed as to avoid the complicated machine operations usually required to carve a receiver out of solid bar stock.

We contemplate that the important functional ladvantages may be achieved by handling the cartridges through a series of passageways which maintain complete control over the cartridge and we believe it to be particularly important that these passages are fairly close iu'diameter to the largest diameter of the cartridge, obviating the chance for cartridges to become misaligned.

We provide a breech bolt which is characterized by a cartridge head engaging stem having an outside diameter only slightly greater, than the outside diameter of the rim of the cartridge head. This bolt stem is arranged to reciprocate in a closely fitting bolt stern guideway which is concentric with and leads directly into the. chamber of the barrel. With the exception of an ejection port the bolt stern Vguideway closely surrounds acartridge placed therein by hand or through feed passageways asV mentioned above. This arrangement insures that such a cartridge will be fed straight into the chamber without opportunity for the misalignment which, in conventional designs, sometimes results in the cartridge being fstemmed or turned crosswise across the mouth of'the chamber and frequently results in lead shaving or other deformation of the bullet.

We contemplate that such a bolt and cartridge feed Vmechanism will be useful both in blowbackautoloading armsand inmanually operated arms. In the first-case 2,824,400 Patented Feb. 25, g

ice

it is necessary only to coupleto the bolt a bolt return spring of suitable characteristics and let the gas pressure exerted on the head of a cartridge in .tiring provide the bolt opening force. In the second case it is necessary to couple to the bolt a manual operating handle of some sort and to provide for locking the bolt in breechclosed position.

For a manually operated arm we provide a locking block which can be positioned between locking surfaces on the bolt and on the receiver and we utilize this locking block as a means of coupling between the breech bolt and a manually operated action bar which serves to lock and unlock the locking block and to reciprocatethe breech bolt.

The exact construction of a preferred embodiment of our invention may be ascertained by consideration of the following detailed description referring to the attached drawings in which:

Fig. l is a longitudinal vertical sectional view taken through the action of a firearm embodying our invention. The mechanism is shown in breech closed position with the hammer cocked but with the chamber empty and with a column of cartridges in the magazine.

Fig. 2 is a view similar to Fig. 1, with the mechanism shown in breech open position ready to feed a cartridge to the chamber. v

Fig. 3 is a view similar to Figs. 1 and 2, with the mechanism shown in partially breech closed position in the act of feeding a cartridge to the chamber.

Fig. 4 is a partial horizontal longitudinal sectional view on the line 4 4 of Fig. 1.

Fig. 5 is a view similar to Fig. 4, with the breech mechanism just unlocked from the receiver.

Fig. 6 is a vertical cross-sectional view on the line 6 6 of Fig. 1.

Fig. 7 is a vertical cross-sectional view on the line 7 7 of Fig. 1.

Fig. 8 is a vertical cross-sectional view on the line 8 8 of Fig. 1.

Pig. 9 is an enlarged partial longitudinal vertical sectionalview in the same plane as Fig. l but including only the barrel and receiver to more clearly illustrate the cartridge feed passages.

Fig. 10 is a left hand elevational view of the barrel and breech bolt assembly.

Fig. 11 is an enlarged partial horizontal longitudinal sectional viewlon the line 4 4 and, except for the enlarged scale, corresponds to a portion of Fig. 4.

Referring to the drawings by characters of reference, it will be seen that the invention is embodied in a slide action magazine firearm having a barrel 1, a receiver 2, and a buttstock 3 as basic structural units. A fire control assembly 4, conveniently that of the patent above referred to, is supported in the receiver and a breech bolt 5 is guided for reciprocation in the receiver. Beneath'the barrel 1 a conventional tubular magazine 6 is supported and a fore-end 7 is slidably supported thereon. An action bar 8 is provided to couple the sli-dable foreend to the breech bolt, permitting manual operation of the action.

. The receiver 2 of this construction is conveniently an aluminum die casting permitting a relatively intricate shape with a minimum of machining and with great economy in use of material since so little of the material need be converted to useless chips in the manufacturing process.

The barrel 1 extends rearwardly into the receiver to the plane in which Fig. 6 is taken and is retained there by a hardened takedown screw 9 passing through an eccentric hardened bushing 10 mounted in the forward extension 2a of the receiver and .engaging al hardened fore-end hanger 11 secured rigidly to the barrel and providing a support for the rear end of the tubular magazine. By locating the hole for the takedown screw eccentrically in the bushing, a means is provided for effecting an initial adjustment of the position of the barrel in the receiver by rotation of the bushing, which adjustment may thereafter be maintained by staking the eccentric bushing in a fixed position in the receiver. The bushing also effectively increases the load bearing area of the aluminum receiver and insures that the receiver will not be deformed by loads encountered in use of the rifle.

The breech end of the barrel 1 is formed to define a bolt stem guideway 12 having a diameter only slightly, if at all, greater than the normal head diameter of the cartridges to be used therein and with the usual chamber 13 to support the cartridge lduring firing. The bolt 5 is provided with a cartridge head engaging stem 14 which in the breech locked, or firing position shown in Fig. l and 4, substantially completely fills the bolt stem guideway and supports the head of a chambered cartridge. The means for locking and reciprocating the bolt will be separately discussed below. The breech end of the barrel is also formed to define an ejection port 15 in alignment with an ejection port 16 in the receiver and communicating with the bolt stem guideway. There are also formed in the breech end of the barrel certain cartridge feeding passages, also described in more detail later, which communicate between the bolt stem guideway and a track 17 formed in the receiver to receive cartridges urged by the magazine spring 18 and flexible follower 19 to pass from the breech end of the tubular magazine.

The fire control assembly 4 is described in detail in the patent referred to and will be -only briefiy referred to here. Its important elements are a hammer 20 controlled by a sear 21 and a trigger 22, the trigger being disconnected from the sear as a function of the fall of the hammer. An action bar lock 23 is also operated by the fall of the hammer and a manual release arm 24 is provided for the action bar lock, the function of the action bar lock being more fully described relative to breech bolt locking. The fire control assembly provides a convenient mounting base for a cartridge carrier 25 which is under the control of the breech bolt as will be described relative to cartridge feeding and is urged by a carrier spring 26 to assist in the feeding of a cartridge from the magazine to the chamber.

Cartridge feeding As best seen in Fig. 9, the cartridge feeding passages in the breech end of the barrel include an upwardly and rearwardly extending groove 27 which together with the track 17 formed in the receiver define an upwardly and rearwardly extending passage receiving cartridges from the tubular magazine and intersecting the bolt stem guideway to an extent such that an arcuate upper portion of the head of the rearmost cartridge in the passage can project slightly into the lower portion of the bolt stem guideway in the path of the bolt stem. Extending forwardly from the intersection of the groove 27 with the bolt stem guideway is a slot 28 which at its front end 28a and rear end 28b is defined by planar walls separated by a space greater than the diameter of the body of a rimmed cartridge but less than the head diameter thereof. The mid-portion of the slot has a width slightly greater than cartridge head diameter and is defined by a pair of part circular cuts defining opposed forwardly and upwardly inclined tracks 29 which will engage the rim on the head of a cartridge and raise it upwardly under complete control as the cartridge is pushed forwardly.

The receiver is vertically slotted through the bottom of the track 17 to permit movement of the carrier 25 upward and into the cartridge feeding passages. It will be noted that a cam lug 30 is provided on the carrier Which is overriden by the enlarged head of the bolt 5 so that the carrier is depressed whenever'the breech bolt is substantially in its locked position and at all other times is urged upwardly to the extent permitted by the cartridge in the feed passages. An abutment 31 is formed on the carrier to define the rearmost position which the head of a cartridge may reach, which position is not particularlyk critical provided the head is then to the rear of the enlarged mid-portion of the slot 28 and capable of being raised by the carrier into a position partially intersecting the path of the bolt stern. Obviously that portion of the carrier forward of the abutment 31 should not be longer than the shortest cartridge to be fed from the magazine. An abutment 32 is also formed by the tip of the carrier to oppose rearward movement of following cartridges while one is being fed to the chamber. A detent notch 31a receives the rim of a cartridge and assists in control thereof, as will be later described.

Considering the operation of the cartridge feeding mechanism, we may logically start with Fig. 1 in which the breech is closed on an empty chamber and a cartridge 33 is in the feed passages followed by a cartridge 34 under the urging of the magazine spring. As the bolt is moved rearwardly to the Fig. 2 position, the carrier is freed from restraint by the bolt and urges the head of the cartridge 33 upwardly to the maximum extent permitted by the narrow rearward portion 28b of the slot 28. The engagement of the rim of the cartridge in the detent notch 31a serves as a means of positively preventing an upward displacement of the bullet end of a short cartridge. At the same time, the body and bullet portion of the cartridge are inclined upwardly in the forward narrow portion 28a of the slot and the forward end of the carrier cuts off further movement by the cartridge 34.

As the breech bolt is moved forwardly the bolt stem picks up the projecting arcuate portion of the rim of thecartridge 33 and moves that cartridge forwardly in the slot 28. During this forward movement the enlarged rim at the head of the cartridge encounters the forwardly and upwardly inclined tracks 29 and, with the assistance of the carrier 25, the cartridge head is raised thereby up the face of the bolt stern in position for the rim to be engaged by the claws of the opposed extractors 35 in the bolt stem. As the carrier and the tracks 29 elevate the head of the cartridge, the carrier maintains a lifting pressure on the body of the cartridge, with the result thatthe cartridge is elevated smoothly and in a substantially continuous controlled movement is presented to the chamber in a straight line and without bullet deformation. Because the passages confine the cartridge quite closely there is no opportunity for a bullet to turn upwardly or crosswise and fail to enter or stem the chamber. Fig. 3 illustrates the relationship of the parts about halfway through the cartridge feeding operation.

As the bolt stem seats the cartridge 33 in the chamber the carrier is cammed downwardly by the bolt 5, releasing the following cartridge 34 to the position occupied in Fig. l by the cartridge 33.

Bolt f eciprocaton and locking As previously noted, a slidable fore-end 7 and action bar 8 are provided to reciprocate the bolt 5 in the receiver. Considering first Fig. 10 which shows the barrel assembly after the rifle has been taken down, it will be noted that the action bar extends rearwardly beneath the left hand side of the barrel to a position where it is normally guided by a track 36 formed in the receiver casting. At the rear end of the action bar an upstanding lug 37 is provided which is received in a semi-circular camming cut 38 in the outer face of a locking block 39.

The locking block is received in a groove 40 of roughly dovetail shape extending vertically across the left hand side of the bolt body. The inner face of the locking block (see Figs. 4, 5, and 11) is defined by two at portions 41 and 42 at an angle to each other, the apex of V thatangle forming a center of rotation about which the locking block may rock. In the Fig. 4 and Fig. 11

or locked position, the forward portion 41 of the lockingblock lies on the bottom of the bolt groove and the curved surface 43 of the locking block is received in a locking recess 44 in the receiver side wall, forming a strut which securely holds the bolt against any rearward force which may be exerted thereon. In the Fig. 5 or unlocked position the rearward at portion 42 of the locking block lies on the bottom of the bolt groove and the locking block is wholly confined within the bolt groove. Since, in all locations except that in which the locking recess 44 is formed, the receiver forces the locking block to remain confined within the bolt groove, the engagement of the lug 37 on the action bar with the semi-circular camming cut 38 in the locking block provides a connection for reciprocating the bolt.

In the locked position of Fig. 4, the lug 37 is forward of the camming cut 38, bearing on the surface 41a and securely holding the locking block in locked position, but after a short rearward travel of the action bar the lug enters the camming cut 38 and bears on the rear curved surface thereof, camming the locking block back into the bolt groove. On the return movement of the bolt the lug bears on the forward curved surface of the camming cut 38 and as soon as the locking block is opposite the locking recess 44 in the receiver, a component of the force exerted by the lug 37 acts to swing the tail of the block outwardly, positioning the surface 43 within the locking recess 44 and retaining it there when the lug 37 rides forwardly out of the camming cut 38 onto the surface 41a.

At least theoretically it would seem desirable to form the curved end 43 of the locking block to a radius of curvature identical with that of the locking recess 44. In practice, however, we have found that the locking block tends to indent itself minutely into the surface of the locking recess under the strain imposed by firing the more powerful cartridges. As a result, when the curvature of the surfaces is identical, it is sometimes diicult to unlock the action. We have found that it is desirable to employ a slightly longer radius of curvature for the surface 43 and to center this radius on a line somewhat outside but parallel to the intersection of the planar surfaces 41 and 42, as best shown in Fig. l1. With this relationship every increment of rotation of the locking block about the intersection of the surfaces 41 and 42 tending to unlock the breech results not only in sliding movement of the surface 43 across that of the locking recess 44 but also results in a radial separation of those surfaces making unlocking quite easy. Similarly, upon locking, these surfaces tend to approach each other more closely and the breech bolt is cammed forwardly to its final closed position.

For best results, it is desirable to pre-load the locking system by tiring a cartridge or by any other convenient means, to impress or pre-set the locking block in the recess 44, and then to set the rifle head space to desired standards by adjustment of the eccentric bushing which is thereafter staked in place. With this procedure we have found that head space is maintained within acceptable limits throughout endurance tests involving the firing of many more rounds of ammunition than an average shooter can be expected to expend throughout the period of his use of a rifle.

The difference in the radius of curvature of the surface 43 and of the locking recess 44 is not particularly critical provided the relative relationships indicated above are maintained and further provided that the increase in the radius of curvature of the surface 43 is not so great as to result in an excessive concentration of the locking block load adjacent the corner 44a of the locking block recess. A cutter run-out resulting in a tangential departure of the corner 44a from the right circular conformation of the rest of the recess 44 is helpful in alleviating any tendency to upset in this region of the receiver and makes it easier to approach the theoretically perfect mating surfaces while maintaining the above de scribed relationship which provides for easy openings.

When the rifle is taken down as in Fig. 10, the .locking block is retained in the bolt groove by virtue of the dovetail shape of the bolt groove, the forward wall of which may be substantially a right circular cylindrical surface defined by a radius of the length of the at surface 41. Similarly, the rear wall of the bolt groove may be substantially a right circular cylindrical surface defined by a radius of the length of the at surface 42 of the locking block, and the locking block tail 43a bears on this surface, being limited in the extent of movement permitted by a lip 43b which is turned in to obstruct the path of the tail 43a. The locking block is retained against accidental removal from either end of the bolt groove by means of a hole 45 passing through the locking block and loosely embracing a pin 46 seated in the bolt body. To remove the bolt 5 from the assembly of Fig. 10, it is only necessary to -spring the action bar laterally to force it from the bolt groove and manually remove the bolt, such springing being performed without substantial strain on the action bar which is then deprived of the support of its guide track 36 in the receiver.

The action bar lock 23 previously referred to engages in the conventional way with an abutment 47 on the action bar when the bolt is in locked position to releasably lock the bolt closed. Upon tiring, as described in the patent, the action bar lock is released by the fall of the hammer, permitting instant reloading by pumping the fore-end. Manual release of the action bar lock is provided by the action bar release lever 24, permitting unloading without firing or opening of the action for cleaning or inspection.

For completeness it may be noted that the bolt stem is longitudinally grooved to receive a firing pin 48, the rear end of the tiring pin being exposed in a slot 49 in the bolt to the blow of the hammer 20. A post ejector 50, Figs. 4, 5, and 6, is provided in the bolt stem guideway to intercept the head of a cartridge being extracted and to slip it laterally out of the ejection ports 15 and 16. A portion of the bottom of the receiver casting may be conveniently closed by a receiver cover 51 retained by the reception of spring tabs 52 in a groove cut in the inside wall of the rece1ver.

To insure that the bolt always locks up in the same orientation, we provide a bolt guide pin 53 seated in the receiver and engaging a slot 54 in the top of the bolt to prevent rotation of the bolt upon its own axis as it approaches the locked position. Without this more exact orientation, there might be some tendency for the locking block to engage at an angle and exert excessive unit pressure in some small element of the locking recess 44.

Although the detailed description thus far has dealt specifically with a slide action manually operated arrn, it should be obvious that many of the components would be applicable to other forms of operation. For example, if the locking block and action bar lock were removed from the arm and the action bar coupled at one end directly to the bolt and at the other end to a breech closing spring instead of a manually slidable fore-end, all other elements could remain the same and the arm would function as a blowback operated autoloader. Obviously, the interchangeability of parts between two such companion models results in great economy in manufacture. The claims appended hereto are not therefore to be construed as limited solely to a manually operated firearm but to extend as well to blowback gas operation, and other applicable operating systems.

What is claimed is:

l. In a firearm having a barrel, a receiver and a breech bolt reciprocable therein, breech bolt locking means cornprising in combination a groove formed in and extending across said breech bolt and having a planar bottom surface in a direction transverse to the line of reciprocation of said bolt; a locking block received in said groove and having two mutually inclined surfaces in facing relation to the bottom of said groove, the line of intersection of said .mutually inclined surfaces defining a 'fulcrum about which said locking block yis rockable on ythe'bottom sur- Aface of said groovebetween a first position :in which the block is wholly within the projected surfaces of -the breech bolt adjacent said groove and a second position in which the rearward end of said locking block protrudes laterally from said groove and the forward end of said locking block is in engagement with the -forward wall of said groove; a locking recess in said receiver in which the rearward end of said locking block may be engaged when said locking block is in said second position to secure said breech bolt against rearward movement in the receiver; and means to rock said locking block from said first position to said second position and vice versa.

2. The combination described in claim 1, one of said mutually inclined surfaces being in facial contact with the planar bottom of the groove when said locking block is in said first position and the other of said mutually inclined surfaces being in facial contact with the planar bottom of the groove when said locking block i-s in said second position, said locking block being rockable about the line of the intersection of said mutually inclined surfaces with the planar bottom of the groove.

3. The combination described in claim 2, the rear wall of said groove being formed as a substantially right circular cylindrical surface defined by a radius equal to the length of said one of said mutually inclined surfaces and the rear end of said locking block being formed with a tail engaging with said cylindrical surface; the forward wall of said groove and the forward end of said locking block being formed as interengaging substantially right circular cylindrical surfaces mutually defined by a radius, the center of which is the line of rotation about which the locking block is rocked.

4. The combination described in claim 3, and means provided in said breech bolt vengageable with the locking block to prevent said locking block from sliding from either end of said groove when said breech bolt is removed from said receiver, the inter-engagement of said t, K cylindrical surfaces and the tail of said locking block preventing disassembly Yof said locking blockfby any other movement than sliding `out through an endof said groove. M

5. The combination describedin claim 3, saidmeans to rock the locking block comprising a camming surface formedin the surface of said locking block opposite to said mutually yinclined surfaces, a reciprocable action ba-r, and` a llug on said action bar engageable with said camming-surface.

6. vThe combination described in claim 5, said camming surface being a substantially right circular semi-cylindrical cut in said locking block -deiined by a center line parallel to theline of yintersection of said mutually inclined surfaces -and normal to theline of reciproca'tion of said action bar. Y

7. 'The combination described in claim S6, vsaid'action bar lug being substantially contained within said semicylindrical ycamming cut when said locking block has been turned to said first position to serve as a connection constraining said breech bolt to reciprocate with the action bar while said locking block'remains in said first position.

8. The combination described in claim 7, said 'locking block being provided with a substantially yfiat surface forward of said camming cut and substantially Vparallel to the planar bottom of said bolt groove when said locking block is in said second position, said-action bar lug being releasably engageable with said substantially fiat surface to retain said locking block in said secondposition.

lReferences Cited in the file of thispatent UNITED. STATES PATENTS 2,590,981 Lippert et a1 Apr. 1, 1952 2,756,640 Maillard' July A31, 1956 FOREIGN PATENTS v641,356 Germany Jan. 28, 1937 592,612 Great Britain Sept. 23, 1947 

